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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 552 |
| 7 | 2826 |
| 8 | 17080 |
| 9 | 117816 |
| 10 | 943250 |
| 11 | 8330356 |
| 12 | 82954582 |
| 13 | 915854808 |
| 14 | 11147075946 |
| 15 | 147948526182 |
[1,1,2,6,24,120,552,2826,17080,117816,943250, 8330356,82954582,915854808,11147075946, 147948526182] |